The present invention relates generally to an apparatus for ultrasonic welding and, more particularly, to an apparatus for ultrasonic welding with improved surface finish characteristics.
Ultrasonic welding is well-known in the prior art. During ultrasonic welding, materials are welded together by moving the end of an ultrasonic horn against the material with the frequency that lies in the ultrasonic range. The surface oxide and contaminants are disintegrated and dispelled, and a strong metallic bond is formed. A wide variety of types and configurations of ultrasonic welders are known.
Ultrasonic welding has proved highly beneficial in welding a variety of materials, including light weight materials such as aluminum and magnesium. Conventional fusion-based welding technologies potentially present problems such as dimensional instability, surface finish and heat affected zones when applied to such alternate materials. Although some of these problems can be alleviated using post-welding craftsmanship, the time and cost involved in such repair procedures further underlies the value of ultrasonic welding.
Present ultrasonic welders, as well as conventional fusion based welding, have difficulty achieving class-A surface finishes. Often, in ultrasonic welders, both the sonotrode tip and the anvil of ultrasonic welders are knurled to improved the gripping of material. The knurl pattern leads to imprints on the surface of welded articles. This can be highly undesirable when an unaffected surface appearance of the material is desired, as is often the case in automotive body welding. It is known that this imprint may be reduced through the use of smooth surface tips and anvils. The use of these smooth surfaces, however, often requires a higher clamping pressure during welding to compensate for the reduction of material gripping. This increase in clamping pressure results in indentation at the weld area, which again can lead to a negative surface appearance of the material.
It would, therefore, be highly desirable to have a method of welding that reduces the negative effects on surface finish characteristics of the material it welds.
It is, therefore, an object of the present invention to provide an ultrasonic welder that provides improved surface finish characteristics on weldable material.
In accordance with the object of this invention, an ultrasonic welder is provided. The ultrasonic welder includes an anvil. A fabric element is positioned between the anvil and the weldable material. The fabric element improves the surface finish characteristics of the weldable material contacting the anvil.
Other objects and features of the present invention will become apparent when viewed in light of the detailed description of the preferred embodiment when taken in conjunction with the attached drawings and appended claims.